Detection of analytes in a sample and determination of the chemical composition of a sample are useful in many clinical and scientific applications. Thus, methods, devices, and systems for analyzing samples and for detecting target substances within the samples are useful in many contexts. A method of testing for, or for detecting, a target substance in a sample may be termed an “assay.” Some assays may be performed by devices or systems with little or no human intervention; such assays may be termed automated assays, and are performed by automatic devices or automatic systems.
Clinical assays are often developed to identify target materials in samples taken from patients. For example, targets may include proteins, nucleic acids, lipids, organic molecules, inorganic molecules and ions. Such target materials may include drugs, drug metabolites, vitamins, hormones, growth factors, carrier proteins, cells, infectious agents, and other target materials that may be indicative of medical conditions or disorders. Other clinical assays may be directed to testing for levels of drugs, drug metabolites, hormones, vitamins, or other substances which may be of therapeutic or clinical interest. In some instances, a sample may include multiple analytes, and multiple assays may be required to detect or quantify all of the analytes of interest in a sample.
Clinical assays require samples to be obtained from a subject, such as a patient suffering from, or suspected of suffering from, a disease characterized by markers identifiable by the assay. However, providing samples is often uncomfortable, or difficult, or inconvenient for a subject; the discomfort, difficulty, and inconvenience is typically greater the larger the volume of sample that is required.
Accordingly, methods and devices for reducing the volume of sample required to be obtained from a subject are desired, and assays, guidelines and methods for altering existing machines and assays that may be performed on smaller volume samples than presently practiced are also desired.